Solvent refining of hydrocarbon oil



Sept. 8, 1936. F. x. GovERs SOLVENT REFINING OF' HYDROCARBON OIL FiledMarch 2, 1955 .SSR

h ERM@ bw Patented Sept. 8, 1936 PATENT ol-Fics 2,054,052 SOLVENTREFlNlNgIgF HYDBOCABBON;

Francis X. Govers, Vincennes, Ind., signor to Indian Refining ompany, acorporation of Maine Application March 193s, semi No. 9,005 1a claim..(ci. iss-17) This invention relates to the treatment of hydrocarbon oil,and particularly to a method ot treating mineral oil with selectivesolvents. Y

The invention broadly contemplates a process 5 for `solvent reningmineral oil for the production of lubricating oil oi' high viscosityindex, low

pour testf, and other desired properties and char-` acteristics.

'I'he invention comprises extractively treating `l mineral oil stockwith a selective solvent, such as furfural, for example, wherein the oilis separated into an extract phase containing low viscosity indexconstituents of the oil, and a railinate phase comprising highvviscosity index constitul ents of the oil. 'I'he two resulting phasesare separately cooled, to eifect alteration of mutual solubility ofcomponent parts, and centrifuged or settled to remove the componentparts not retained in solution. 'I'he matter thus removed from eachphase is returned, all or in part, to the zone ofextraction wherein itis brought into contact with fresh oil undergoing treatment.

In the treatment of wax-bearing oil, the railinate phase, containingsubstantially all of the parain constituents of the oil, is dewaxed, as

will be more fully described, by means oi.' selective dewaxing solventsto produce therefrom a lubricating oil of low pour test and highviscosity index. In the solvent treatment of mineral lubricating oilstock with furfural, solvent action increases with elevatedtemperatures, and the selectivity increases with lower temperatures;thus, at 250 F. the total solvent power of the furfural is far greaterthan at 80 F. but the selectivity is greater at 80 F. than at 250 F.Economy, based alone on the amount of solvent used, predicates the useof high temperature, and economy based on percentage yields of highviscosity index oils 40 predicates the use of low temperatures.

I have discovered that furfural is quite selective, even at hightemperatures, when saturation points for any particular constituent orcomponent part of the mineral oil stock are not ex- I have discoveredthat by the proper use of limited amounts of furfural at hightemperatures, extraction refining can be practiced economically in sucha way as to eiect maximum 50 action of solvent rening with minimum lossof desirable constituents while at the same time increasing thesusceptibility of the ralnate phase to the refining action of certainsolvents for still further improvement in color, viscosity 55 index,sulphur, and Conradsen carbon.

I have discovered that the oils separated from the cooled extract phaseare more susceptible to solvent rening than-the original stock.

I have discovered that the raiilnate phase, when cooled and separatedfrom the Aretained 5 extract phase, is highly susceptible to the solventretlning action of ketones, such as methyl ethyl ketone and methylisobutyl ketone. K

:I have discovered that this process, when practiced in the order o1'the steps herein disclosed, 10 will, from any given wax-bearinglubricating stock, give higher percentage yields of low pour test oilsof any given viscosity index with resultant lighter specic gravity,lower Conradsen carbon, lower sulphur, and better color, without 15treatment with mineral acid, than any solvent` process heretoforedescribed.

I have discovered that the process, when practiced in the order of thesteps as herein disclosed, is particularly. advantageous in thetreatment of 20 either heavy distillates, or residual oils.

I have discovered that the ramnate can be dewaxed by means of aselective solvent comprising in part the selective washing or reningsol- .ventused inl the last step of extraction, and that 25 the iinalresult is increased yields of low pour test, high viscosity index oilsof very low Conradsen carbon and sulphur.

Accordingly, the invention comprises a process for treating wax-bearinglubricating oil stock 30 in which the oil is extracted with a solventcomprising furfural at temperatures of around 170250 F., and the mixtureseparated into extract and raffinate phases respectively. The extractphase will contain low viscosity index undesirable constituents, blendedwith a certain amount of desirable relatively higher viscosity indexconstituents. 'I'he rainate phase will comprise the relatively higherviscosity index constituents of the oil containing some of the ex- 40tract phase retained or suspended therein.

The two pl'ases are separated from each other. The raffinate phase iscooled and subjected to centrifuging or settling to separate theseretained extract phase bodies. The extract phase is cooled, to releasefrom solution, and subjected to centrifuging or settling to separatepart of the desirable relatively higher viscosity index constituents.The separated bodies are then returned, all or in part, to theextraction zone where they are brought in contact with fresh charge.

When oil is extracted with furfural at elevated temperatures, as forexample around 17o-250 F., the resulting ramnate phase contains anappreci- -able amount oi' extract phase material retained therein, andlikewise the extract phase also retalus a substantial amount ofrelatively higher viscosity index oil which, at the high temperatureprevailing, is soluble in the solvent. Accordingly, by cooling theraiilnate phase down to a temperature below 170 F., or in the range of13D-150 F., depending upon the pour test oi' the oil. and uponcentrifuging the thus cooled rafllnate phase, a substantial portion ofthe retained extract phase material may be separated from the ralilnatephase. Similarly, in the case of the extract phase, upon cooling forexample to about 110 F. and standing at this temperature, a substantialquantity of oil separatcsfrom solution.

The extract phase material, separated from the raillnate phase in theforegoing centrifuging step, comprises furfural containing oil dissolvedthereinl. 'I'his material may be returned to the extraction zone or bemixed with fresh charge entering the extraction zone.

It is of advantage also to return the oil separated from the cooling ofthe extract phase to the extraction zone. This oil is of a relativelyparafiinic natureand its addition to the fresh charge has a tendency toincrease the selectivity of the extraction solvent or to facilitate theseparation of the oil into extract and rainate phases, respectively richin low viscosity index and high viscosity index constituents of the oil.

Consequently, by returning the extract phase material separated from theraffinate phase, and the oil separated from the extract phase, to theextraction zone, advantage is taken of the furfural retained thereinsince it is thus used in the further extraction of fresh oil. It alsoenables the obtaining of higher ultimate yields of high viscosity indexoil since the oil constituents contained in the separated material aresubjected io further separating action.

The railinate phase, after centrifuging, will still retain some extractphase material, and this and other undesirable constituents are removedby subjecting the raffinate phase to a washing treatment with a solventadapted to Y effect their removal. Such a solvent may comprise, forexample, a. ketone such as methyl ethyl ketone, methyl isobutyl ketoneor homologs.

When the oil undergoing treatment comprises a wax-bearing oil, thesubsequent dewaxing operation is effected by means of a selectivesolvent mixture comprising, for example, a mixture of an anti-solventliquid of the character of an aliphatic ketone, such as acetone ormethyl ethyl ketone, and a good oil solvent such as benzol or toluol.The wax anti-solvent liquid component ofthe dewaxing solvent mixtureadvantageously comprises a solvent which is also suitable by itself as awashing solvent capable of dissolving from the raflinate phase anyextract phase material remaining therein.

I have found that methyl ethyl ketone, for example, is a suitablesolvent for this purpose. Thus, in carrying out the process of myinvention, as applied to a wax-bearing oil, the resulting rafilnatephase, after cooling and -centrifuging to remove extract phase material,is then subjected to washing with methyl ethyl ketone.

In this washing step, the methyl ethyl ketone dissolves any remainingextract phase material retained in the cold railinate phase, and which'may comprise furfural as well as low viscosity index oil. Otherimpurities in the oil, insoluble' or sparingly in the furfural, as forexample sulphur compounds and other bodies which tend to form color orto produce residual carbon, will also be removed by the washing solvent.

In washing the raillnate with the wash solvent, there results aseparation into two phases. One phase will comprise the solution of washsolvent liquor, furfural, color forming matter and undesirableconstituents dissolved from the raffinate phase, while the other phasewill comprise the puried ramnate phase in a suspended nely dividedcondition. These two phases can be separated by filtration. The ltercake, comprising the washed raffinate phase will, in the case of theabove wax-bearing oil, contain wax constituents and, therefore, theretained wash solvent, namely, methyl ethyl ketone, is left mixed withthe washed raffinate phase to serve as a component of the subsequentdewaxing solvent mixture.

Accordingly, an additional quantity of methyl ethyl ketone, togetherwith sulcient benzol or toluol, is added to the washed rafilnate toproduce a solvent mixture which has selective action as between oil andWax at temperatures of the order of F. and below. This mixture is thenchilled to precipitate the Wax and the precipitated wax constituentsremoved therefrom by ltering, centrifuging, settling or other mechanicalmeans. After removal of the solvent from the dewaxed oil, the oilisnished up, for example, by contacting with solid adsorbent material toproduce a finished lubricating oil product of superior characteristics.

In order to more clearly describe the invention, reference will now bemade to the accompanying ow diagram which illustrates the practice ofthe process of my invention as applied to the treatment of wax-bearingoil such as a waxbearing lubricating distillate derived from Mid-Continent crude.

The wax-bearing oil to be treated is conducted from a storage tank l anddelivered by a pump through a pipe 2 to the lower portion of theseparator 3.

The separator 3 comprises a vertical, cylindrical vessel provided withagitation means 4, as shown. The separator and agitating means areadvantageously of the type described in my copending application Ser.No. `1,331, led January 11, 1935.

The oil may be heated to suitable temperature prior to introduction tothe separator 3 in which case it is passed through a heater 5. Where itis not necessary to thus heat the oil, it may be by-passed around theheater 5, as indicated in the flow diagram.

The furiural is conducted from a tank 6 through pipe 1 to the upperportion of the separator 3. As in the case of the entering oil charge,the furfural may be heated by passage through a heater 8 prior tointroduction to separator 3. The amount of heating to which the solventand oil is subjected will depend upon the particular temperaturecondition which it is desired to maintain within the separator 3 and itis contemplated that all of the heat may be supplied either by heatingthe oil or by heating the furfural alone.

The furfural being heavier than the oil flows through the separator 3countercurrently to a rising body of oil. Intimate contact between theoil and solvent is brought about by rotation of the agitating means 4.As a result of the contact between oil and solvent within the separator,the mixture separates into extract and ramnate phases respectively. Theextract phase i The resulting chilled extract phase is then conducted toa settling chamber II wherein, upon standing at the above temperature,paraillnic oil separates from the mixtureand is drawn off to a tank I2.It is to'be understood that instead of settling, the cooled extractphase may, of course, be subjected to centrifuging if desired.

'I'he remaining extract phase from which the paraillnic oil has beenseparated is then drawn to a tank I3 wherein it may be stored for suchfurther treatment as may be desired.

The raillnate phase formed in the separator 3, and which rises to theupper portion of the separator, is withdrawnv therefrom through pipe I4to cooler I5 wherein it is cooled to a suitable temperature above thesolidifying point of the waxbearing raflinate'oil. This temperature willdepend upon the proportion of wax present as well as upon the viscosityof the oil.

The cold raflinate phase is then delivered to a centrifuge or otherseparating means, such as a settling chamber I 6, wherein the extractphase material retained therein is separated. The thus separated extractphase material is conducted to a tank I1 for return to the separator 3,as will be subsequently described.

The centrifuged raffinate phase is then mixed in a mixer I3 with aboutequal volume of methyl ethyl ketone drawn from a tank I8. This mixing iscarried out advantageously at a temperature just sufficient to completesolution of the railnate phase in the methyl ethyl ketone.

From the mixer I9, it is passed through a chiller wherein it is chilledto a temperature of around 30 F. At this temperature, the parafnicconstituents or the oil, including parain wax, will be converted to asubstantially solid form.

This cold mixture is then conducted to a filter 2l wherein the liquid isseparated from the solid matter. The liquid or filtrate will comprisemethyl ethyl ketone containing in solution extract material dissolvedfrom the railinate phase, as well as other undesired impurities freelysoluble in methyl ethyl ketone but sparingly soluble in furfural,including sulphur compounds, colorforming, as well as residualcarbon-forming bodies.

The separated liquid or filtrate is withdrawn from the illter 2l andconducted to a still 22. The methyl ethyl ketone is vaporized from thisliquid, and the resulting vapors cooled and condensed in a cooler 23,and from there returned to the tank I8, previously mentioned.

The residual liquid remaining in the still 22, comprising furfural andoil, is withdrawn to tank 24. From this tank, it is returned to theseparator 3 directly, or else ilrst mixed with fresh charge, as will besubsequently described.

The filter cake comprising parafilnic bodies of the oil, including wax,remaining in the filter 2|, is withdrawn through a pipe to a mixer 26.Prior to introduction to the mixer, this paraillnic oil is mixed with anadditional quantity of methyl ethyl ketone, from the tank I8, and alsowith benzol drawn from a tank 21. The methyl ethyl ketone and benzol areadded in the proportions of about 40% ketone to 60% benzol, and mixedwith the oil in the proportion of 3 to 4 parts of solvent mixture to 1part of oil.

From the mixer 26 the oil and solvent is conducted to a chiller 28wherein it is chilled to a temperature of around 10 F. in order toprecipitate the wax from the solution.-

The chilled mixture is then conducted to a illter 23 wherein theprecipitated wax is separated The lter cake is removed and -4 as aillter cake. the solvent recovered from the wax. The dewaxed ltrate isthen delivered to a still 30 for removal of the solvent which latter maybe returned for use in dewaxlng further oil.

The dewaxed oil, free from solvent, is conducted to a contact vessel .3Iwhere it is advantageously contacted with adsorbent clay in the presenceof steam at temperatures of around 40G-500 F. The contacted oil is thendelivered to lter 32 for removal of the solid adsorbent materialtherefrom. The resulting illtrate, comprising finished lubricating oilof low sulphur and low carbon residue content and high viscosity index,coupled with low pour test, is delivered to a tank 33. f A

`The separated oil of paraillnic nature accumulating in tank I2,together with the extract phase material accumulating in tank IT and themixture of furfural and oil in tank 24, is drawn off to a pipe 34. Thiscombined material is then delivered by a pump 35 to the pipe 2,previously referred to, and wherein it is mixed with fresh oil enteringthe lower portion of the separator 3. Instead of combining this materialin this way, those portions accumulating in tanks I'I andA 24 may bereturned directly to the upper portion of the separator 3.

The nature and amount of oil which is separated from the rafnate andextract phases in the foregoing operation may be illustrated byreference to the following data obtained in the solvent refining of awax bearing distillate having the following characteristics:

Gravity A. P. I 25.4 Viscosity Saybolt universal at 130 F 143 ViscositySaybolt universal at 210 F 50 Carbon residue .16% Viscosity index. '7l

there resulted a separation of a lower layer ofmaterial comprising about2% oil and 98% furfural. This lowerlayer was removed, and the oil andsolvent separated. The oil thus obtained from this lower layer amountedto about .07% of the total railnate oil. The solvent was also removedfrom the upper layer comprising raiiinate oil, and the following is atabulation of the tests on this raflinate oil of the upper layer and ofthe separated oil in the lower layer:

Raiinate oil Separated oil Gravity A. P. I Viscosity Sayboltuniversal'at 100 F.. Viscosity Saybolt universal at 210 F. Carbonresidue Viscosity index 97 olor 90V" cell Similarly, when the extractphase was cooled to 130 F. there resulted a separation of oil comprisingabout 1.65% of the extract phase. The tests on this oil, after thesolvent had been removed, were as follows:

Gravity A. P. I 24.9 Viscosity Saybolt universal at l100 F 331 ViscositySaybolt universal at 210 F 51 Viscosity index 67.5

It will be observed fromthe foregoing that the cycle oil thus separatedfrom the extract phase is very similar in character to the original waxdistillate prior to extraction and thus contains a substantial portionof valuable oil.

The process of this invention is not restricted to any specific solventor mixture of solvents, but it is contemplated that other solvents ormixed solvents, possessing the desired selective action as betweenconstituents of the oil of differing viscosity index or between solid orliquid constituents of the oil, may be used. While the process of myinvention is particularly adapted to extraction with solvent of thecharacter of furfural, at elevated temperatures, the process isnevertheless applicable to operations in which the oil is extracted withother solvents, such as nitrobenzene, aniline etc., since, as I havealready indicated, centrifuging of the resulting extract and radin-atephases permits therefrom separation of material retained in each phaseymethyl ethyl ketone, as many undesired impurities and constituents arethus rendered soluble in the wash solvent without affecting itsselective action on the high viscosity index constituents.

Also, as regards the dewaxing step, solvents other than methyl ethylketone and benzol may be employed. For example, it has been found thatmethyl isobutyl ketone may be substituted for methyl ethyl ketone sincethis solvent not only possesses anti-solvent properties of wax, but isalso adapted as a wash solvent for removal from the raffinate phase andremaining extract phase material retained therein. Either one of thesesolvents may be employed in conjunction with benzol or toluol, or amixture of benzol and toluol, to provide a selective dewaxing solventmixture.

The process of this invention is not limited to any particular type ofhydrocarbon oil or petroleum fraction. It is adapted to the treatment ofeither distillate or residual fractions of petroleum, and while theinvention has been described as to the separation of wax from waxbearinglubricating oil stocks, it is contemplated that it may also be employedfor the separation of oil from petrolatum or other waxy concentrates.

Moreover, it is contemplated that, as regards the specic manner in whichthe invention is practiced, temperatures and proportions of solvent mayvary from those mentioned above. In the case of dewaxed oils, orrelatively less viscous oils, lower extraction temperatures may beemployed. The extraction of the oil with the selective solvent may becarried out in either a continuous or stage countercurrent operation.

Extraction by the batch method of operation may also be employed.

Obviously, many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, but only such limitations should be imposed as areindicated in the appended claims.

I claim:

1. In the process of rening mineral lubricating oil with a selectivesolvent to produce therefrom a lubricating oil of high viscosity index,the method which comprises extracting the oil with a selective solventto remove low viscosity index constituents as an extract phase andproduce a rainate phase comprising high viscosity index oiland retainingsome extract phase, removing the raffinate phase, centrifuging theraffinate phase to remove retained extract phase material, and washingthe centrifuged raninate phase with a -liquid having the solventcharacteristics of methyl ethyl ketone to remove remaining retainedmaterial.

2. In the process of refining mineral lubricating oil with a selectivesolvent to produce therefrom a lubricating oil of high viscosity index,the method which comprises extracting the oil with a selective solventto remove low viscosity index constituents as an extract phase andproduce a rafnate phase comprising high viscosity index oil andretaining some extract phase, removing the raffinate phase, centrifugingthe ranate phase to remove retained extract phase material, washing thecentrifuged rainate phase with a liquid having the solventcharacteristics of methyl ethyl ketone to remove remaining retainedmaterial, removing the wash solvent containing dissolved matter,separating the solvent from the dissolved material and returning thesaid material to the extraction zone.

3. In the process of refining mineral lubricating oil with a selectivesolvent to produce therefrom a lubricating oil of high viscosity index,the method which comprises extracting the oil with a solvent comprisingfurfural, in an extraction zone at a temperature of around 200 F.,forming an extract phase comprising 10W viscosity index constituents ofthe oil dissolved in the solvent, and a raffinate phase comprising highviscosity index constituents of the oil and retaining some extractphase, separating the two phases, cooling the rainate phase to atemperature below the extraction temperature, centrifuging the cooledranate phase to separate retained extract phase material, and washingthe centrifuged rafhnate phase with a liquid having the solvent charac,-teristics of methyl ethyl ketone to remove remaining retained material.

4. In the process of refining mineral lubricating oil with a selectivesolvent to produce therefrom a lubricating oil of high viscosity index,the method which comprises extracting the oil with a solvent comprisingfurfural, in an extraction zone at a temperature of around G-250 F.,forming an extract phase comprising low viscosity index constituents ofthe oil dissolved in the solvent, and a raffinate phase comprising highviscosity index constituents of the oil and retaining some extractphase, separating the two phases, cooling the rainate phase to atemperature below the extraction temperature, centrifuging the cooledraffinate phase to separate retained extract phase material, returningthe separated material to the extraction zone, washing the centrifugedrafnate phase with a liquid having the solvent characteristics of methylethyl ketone to remove remaining retained material, removing the Washsolvent and dissolved material, separating the solvent from thedissolved material, and returning said'dissolved material to theextraction zone.

5. In the process of reiining wax-bearing mineral lubricating oil with aselective solvent to produce therefrom a lubricating oil of highviscosity index, the method which comprises extracting the oil withfurfural at a temperature substantially n above atmospheric temperatureto remove low viscosity index constituents as an extract phase andproduce a raiiinate phase comprising high viscosity index constituentsand retaining some extract phase, removing the raihnate phase, coolingthe raflinate phase to a temperature below the extraction temperature toseparate retained extract phase material, removing the thus separatedmaterial, washing the remaining raflnate phase with a solvent having thesolvent characteristics of methyl ethyl ketone to remove remainingretained material, and dewaxing the washed ramnate phase.

6. In the process of refining wax-bearing mineral lubricating oil with aselective solvent to produce therefrom a lubricating oil of highviscosity'index and low pour test, the method which comprises extractingthe oil with a. solvent comprising furfural, at a temperature of 150-250F., while at such temperature forming an extract phase comprisingdissolved oil of low viscosity index and retaining some oil ofintermediate character as regards viscosity index, and a railnate phasecomprising high viscosity index constituents of the oil and retainingsome of the extract phase, separating the two phases, cooling therahnate phase to a temperature just above that at which it solidies,centrifuging the cooled rafnate phase to remove retained extractfphasematerial, washing the centrifuged raffinate phase V with a solventhaving the solvent characteristics or methyl ethyl ketone to removeremaining retained extract phase material, removing the wash solvent anddissolved bodies, and dewaxing the washed raiiinate phase.

7. in the process of refining wax-bearing min-r` eral lubricating oilwith a selective solvent to produce therefrom a lubricating oil of highviscosity index and low pour test, the method which comprises extractingthe oil with a solvent having at a temperature of 150 F. and above theessential selective action of furfural as between constituents of theoil of differing viscosity indices, forming an extract phase containinglow viscosity index constituents dissolved in the solvent, and a ramnatephase comprising high viscosity index constituents including wax andretaining some extract phase, removing the rafflnate phase, centrifugingthe rafnate phase to remove retained extract phase material, washing thecentrifuged raffinate phase with a liquid having the solventcharacteristics of methyl ethyl ketone to remove remaining retainedmaterial, and dewaxing the washed rafnate phase inthe presence of achilled solvent mixture having selective action as between solid andhigh viscosity index hydrocarbons and having as a component part of sucha chilled solvent mixture the wash solvent liquid retained by theraffinate phase.v

8. In the process of refining wax-bearing mineral lubricating oil with aselective solvent to produce therefrom a lubricating oil of highviscosity index and low pour test, the method which comprises extractingthe oil with a solvent comprlsingurfural in an extraction zone at atemperature around 200 F., forming an extract phase containing lowviscosity index constituents dissolved in the solvent, and a raiiinatephase comprising high viscosity index constituents including wax andretaining some extract phase, removing the railinate phase, cooling theraftinate phase to a temperature below the extraction temperature,centrifuging the cooled railinate phase to remove retained material,washing the centrifuged rainate phase with a liquid having the solventcharacteristics of methyl ethyl ketone, to remove remaining retainedmaterial, returning the retained material separated from the raffinatephase during the centrifuging and washing steps to the extraction zone,and dewaxing the washed raihnate phase in the presence of a chilledsolvent mixture having selective action as between solid and highviscosity index hydrocarbons and having as a component part of such achilled solvent mixture the wash solvent liquid retained by the railnatephase.

9. In the process of rening mineral lubricating oil with a selectivesolvent to produce therefrom a lubricating oil oi high viscosity indexand low pour test, the method which comprises extracting the oil inanextraction zone at a temperature substantially above atmospheric witha solvent having at a temperature of 150 F. and above the essentialselective action of furfural as between constituents of the oil ofdiffering viscosity indices, forming an extract phase containing lowviscosity index constituents dissolved in the solvent and retaining someoil of intermediate character as regards viscosity index constituents ofthe oil and a raiiinate phase comprising high viscosity indexconstituents and retaining some of the extract phase, separating the twophases, separately cooling the two phases to separateretained material,removing the thus separated material, washing the rafiinate phase Y witha solvent having the solvent characteristics Y of methyl ethyl ketone toremove remaining retained material and returning the retained materialsseparated from each phase to the extraction zone.

i0. In the process of reiining wax bearing mineral lubricating oil witha, selective solvent to produce therefrom'a, lubricating oil of highviscosity index and-low pour test, the method which comprises extractingthe oil in an extraction zone at a temperature above atmospheric with asolvent having at a temperature of 150 F. and above the essentialselective action of furfural as between constituents of the oil ofdiffering `viscosity indices, forming an extract phase containing lowviscosity index constituents dissolved in the solvent and retaining someoil of intermediate character as regards viscosity index, and araiiinate phase comprising high viscosity index constituents of the oiland retaining some of the extract phase, separating the two phases,separately cooling the two phases to separate retained material,removing the thus separated material, washing the raflinate phase with asolvent having the solvent characteristics of methyl ethyl ketone toremove remaining retained material and returning the retained materialsseparated from each phase to the extraction zone, and dewaxing therailinate phase in the presence of a chilled solvent mixture havingselective action between solid and high viscosity index hydrocarbons andhaving as a. component part of such chilled solvent mixture the washsolvent liquid retained by the washed raffinate phase.

eral lubricating oil with a selective solvent to` produce therefrom alubricating oil of high viscosity index and low pour test, themethod'which comprises extracting the oil in an extraction zone with asolvent comprising furfural, at a temperature in the range of 15G-250F., whiie at such temperature forming an extract phase comprisingdissolved oil oi low viscosity index and retaining some oil ofintermediate character as regards viscosity index, and a ramnate phasecomprising high viscosity index constituents of the oil and retainingsome o the extract phase, separating the two phases, separately coolingthe two phases to a temperature substantially below the extractiontemperature, centrituging the cooled raiilnate phase to remove retainedextract phase material, settling the cooled extract phase to removeretained relatively high viscosity index oil, washing the centrifugedraillnate phase with a solvent having the solvent characteristics ofmethyl ethyl ketone adapted to remove remaining retained extract phasematerial, returning the bodies separated from the two phases to theextraction zone, and dewaxing the washed rafilnate phase.

12. In the process of reilning wax bearing mineral lubricating oil witha selective solvent to produce therefrom a lubricating oil of highviscosity index and low pour test, the method which comprises extractingthe oil with a solvent comprising iurfural, at a temperature in therange of 15G-250 F., while at such temperature forming an extract phasecomprising dissolved oil of low viscosity index and retaining some oiloi intermediate character as regards viscosity index, and a raffinatephase comprising high viscosity index constituents of the oil andretaining some of the extract phase, separating thev two phases,

40 cooling the raillnate phase to a temperature substantially below theextraction temperature, centrifuging the cooled rafnate phase to removeretained extract -phase material, washing' the centrifuged rafnate phasewith a liquid having the solvent characteristics of methyl ethyl ketoneto remove remaininglimpurities, and dewaxing the washed rafnate phase inthe4 presence of a chilled solvent mixture having selective action as`between solid and high viscosity index hydrocarbons and having as acomponent part of such charged solvent mixture the wash solvent liquidretained by the high viscosity index constituents.

13, In the process of refining wax-bearing mineral lubricating oil witha selective solvent to produce therefrom a lubricating oil of highviscosity index and low pour test, the method which comprises extractingthe oil with a solvent comprising furfural, at a temperature in therange of 15G-250 F., while at such temperature forming an extract phasecomprising dissolved oil of low viscosity index and retaining some cilof intermediatev character as regards viscosity index, and a rainatephase comprising high viscosity index constituents of the oil andretaining some of the extract phase, separating the two phases, coolingthe raffinate phase to a temperature substantially below the extractiontemperature, lcentrifuging the cooled raiinate phase to remove retainedextract phase material, washing the centrifuged ralnate phase withmethyl ethyl ketone to remove remaining impurities, mixing with thewashed rafnate phase further methyl ethyl ketone together with amodifying solvent of the character of benzol, in proportions such thatthe solvent mixture has selective action as between solid and liquidhydrocarbons at temperatures of the order of 0 F., chilling theresulting mixture to precipitate the wax and separating the thusprecipitated wax and removing the solvent liquids from the dewaxed oil.

FRANCIS X. GOVERS.

